Sewing-machine



(No Model.) 2 Sheets-Sheet 1.

H. H. -BUPIUM- SEWING MACHINIL No. 570,902. Patented Novl 10, 1896.

(No Model.) l 2 sneens-sneet-z. Y H. H. BUPFUM,.

SEWING MAGHINB. Y i i No. 570,902. Patentd Nov. 10A, 1896.Y

may

" UNITED STATES PATENT OFFICE0 HERBERT H. BUFFUM, OF ABINGTON, MASSACHUSETTS, ASSIGN OR TO THE STEAM HEATED HORN COMPANY, OF PORTLAND, MAINE. I

SEWING-MACHINE.

SPECIFICATION forming part of Letters Patent No. 570,902, dated November 10, 1896.

I Application filed, .Tune 24, 1895. Serial No. 553,837. (No model.)

To a/ZZ whom it may concern.:

Be it known that I, HERBERT H. BUEEUM, of Abington, county of Plymouth, State of Massachusetts, have invented an Improvement in Sewing-Machines, of which the following description, in connection with the accompanying drawings, is a specification, like letters on the drawings representing like parts.

The present invention relates to an improvement in sewing-machines, and is applicable to the well-known McKay sewing-machine, in connection with which it will be hereinafter shown and described.

The invention consists in an improved mechanicalV connection between the drivingshaft and the needle-bar-actuating lever, its object being to produce a relatively slower movement of the needle near the ends of its strokes, both up anddown, and a relatively more rapid movement near the middle part of itsstroke than is produced by the actuating mechanism therefor heretofore commonly used. By thus reducing the speed of movement of the needle near the end of its stroke the laying of the thread in the hook by the whirl is rendered more certain and the tightening of the last stitch is effected with less of a jerk and sudden strain on the thread, thus improving the operation of the machine and also improving the quality of the sewing.

, The change in the relative speed of movement of the needle in diiferent portions of its stroke is accomplished in accordance with the present invention by connecting the usual eccentric rod or pitman which actuates the needle-lever with said lever by devices which in eifect change the position of the point of application of the force from said pitman on said lever with relation to the fulcrum of the lever, so as to correspondingly change the effectivelength of the lever-arm during the reciprocation of the said pitman. The arrangement is such that the pitman operates upon the greatest length of lever-arm when at or neai` the ends of the stroke, thus causing the opposite end of the lever which carries the needle-bar to move a shorter distance in a given time, the movement, therefore, being slower, and conversely the pitman acts upon a shorter length of lever-arm during the middle part of its stroke, thus accelerating the movement of the needle during themiddle part of its strokes, both up and down.

Figure l is aside elevation of a sufficient portion of a McKay sewing-machine to illustrate the present invention; Fig. 2, a rear elevation of the portion thereof to which this Vinvention relates, showing the driving-shaft, the reciprocating rod or pitman carried thereby, and the connection between said pitman and the needle-bar lever; and Fig. 3, a diagram view showing the relative positions of the parts in different positions of the needle, dotted lines of different character being used to show the relations at the middle position and both end positions of the needle-bar, respectively.

As has been stated, the construction of the main portions of the machine is well known, and therefore needs no detailed description in connection with the present invention, which consists in a novel construction of the actuating mechanism for the needle-shaft .lever a, fulcrumed at a2 and connected at a3 by the link a4 with the needle-bar a5 in the usual manner. The said lever is arranged to reciprocate the needle-bar by a rocking movement on the pivot a2, and such movement is caused by means of a rod or pitman b, which may be the same as heretofore used in these machines, and is reciprocated by means of the usual eccentric b2 upon the main shaft B of the machine. The connection between said pit-man b and the lever a is made in accordance with the present invention by a link c, connected at c2 to the lever a and at c3 to the rod b, the end thereof which is pivoted at c3 being connected with a movable guide, in this case shown as a link or radius bar d, pivotally supported at one. end in a bracket or extension d2 from the, frame of the machine and pivotally connected atits other end with the rod or pitman b. As the rod b moves up and down, therefore, in;` re; sponseto the action of thel eccentric thelink d will move on an arc, as indicated in Fig,` 3, thus carrying the upper end of the pitmanibtoward the fulcrum cof the lever in ythe* IOO middle'part of the strok,e, thus practically shortening the arm of lsaid lever and-accelerating the movement of the opposite end thereof during the middle part of the stroke and correspondingly reta'rding the movement near the ends of the strokes, both up and down.

The axis or fulcrum cl3 of the guiding-link or radius-bar d is at an intermediate point between the upper and lower positions of its end that is jointed at c3 to the pitman l), the result being that it throws the said joint farthest inward toward the fulcrum a2 of the needle-bar lever at an intermediate point in its stroke and throws said joint c3 outward or away from said fulcrum co2 in the movement from the middle toward the ends of the strokes in both directions. In other words, the fulcrum d3 of the guiding-link is at the opposite side of the pitman b from the fulcrum a2 of the needle-bar lever a, and is at a distance from the actuating-shaft B approximately equal to the length of the said pitman.

In Fig. l the lever is shown at the end of a complete downward movement of the needle, and the rod b is practically in line with the outer end of said lever, so that as said rod begins to move down it will operate upon the lever-arm of maximum length, causing a slow movement of said lever at first, said movement being gradually accelerated as the movement of the guide CZ carries the pivot c3 toward the fulcrum d2. Following the line of movement of the point c3, as shown in Fig. 3, it will be seen that at about the center of the stroke the said point cis nearest the fulcrum a2, thus giving a maximum speed 0f movement to the lever, and as the rod b continues its movement the point c3 again recedes from the fulcrum a2, increasing the effective length of the lever a and causing the slower movement of the needle.

The retardation of the movement near both ends of the stroke relative to the speed produced by the usual crank or eccentric is of great advantage, that at the end of the downstroke affording more time for the whirl to lay the thread into the hook of the needle, and thus insuring greater certainty of this operation, while the slowing down near the upper end of the stroke causes the thread to be finally drawn tight by a slow, steady, and powerful pull of the needle, so that the machine does better work and with much less liability of breaking the thread than when the needle-bar lever is actuated directly from a pitman, as b, pivotally connected directly to the end of the lever, as has been heretofore the construction in McKay sewing-machines.

As shown herein, the link CZ is mounted upon a transverse shaft (Z3 and is forked, as shown in Fig. 2, the rod b extending upward between the said forks and being connected thereto by means of a pintle c3. The links c are made in duplicate, one of said links being connected to one side of the needle-lever d and the other to the opposite side thereof, the said links extending down to the pivot c3 be- -tween the rod b and the forked extension of the movable guide orlink cl. Thus the end of the lever, the connecting-links, and the guide arm or link d may all fall together, as it were, as they descend in making the upstroke of the needle.

It is obvious that the construction of the variable connection between the pitman and the needle-lever can be varied considerably, while retaining the same essential relations between the same. The specific construction illustrated is of advantage, because it can be readily applied to existing machines, it being necessary only to substitute a new lever for the needle-actuating lever commonly employed and to add the links c, guide-arm d, and supporting-bracket for the latter to the existing machines, said parts cooperating `properly with the same pitman or eccentric rod as employed in connection with the original lever. the guiding mechanism, may be connected with the usual frame over the usual uprights or posts connecting the upper and lower plates of the frame. For this purpose the brackets are secured over the ends of the upriglits by tubular or thimble-like nuts d4, (see Fig. 1,) which takes the place of the nuts commonly employed to fasten the top frame-plate to the uprights. The foot portion of the bracket that rests on the top of the frameplate is preferably provided with an elongated opening d5 to receive the tubular shank of the nut d4, thus enabling the position of the bracket to be adjusted to vary somewhat, if desired, the effect of the guide-arm d in modifying the action of the pitm an b on the lever a.

I claiml. The combination with the needle-baractuating lever of a sewing-machine; of the main shaft and pitman actuated thereby; and means for operatively connecting said pitman and needle-bar lever; and a guide-link pivotally connected at one end with the said pitman and pivotally connected at its other end with the framework at a point on the opposite side of said pitman from the fulcrum of said needle-bar-actuating lever, and at a distance from said main shaft approximately equal to the length of said pitman, whereby the movement of the needle-bar lever is retarded near both ends of the stroke and accelerated in the middle part of its stroke relative to the speed that would be produced if the pitman were directly connected therewith, substantially as and for the purpose described.

2. The combination with the needle-bar-actuating lever; of the main shaft and pitman actuated thereby; a link pivotally connected at one end with the pitman, and at the other end with the needle-bar lever; and a guidelink or radius-bar pivotally connected at one end with the joint between the pitman and link, and pivotally connected at its other end with the frame of the machine, as set forth, said guide-link -causing the joint between the pitman and link to be carried toward the fulcrum of the needle-bar lever during the move- The brackets d2, which support IOO IIO

570,902 l l l s ment from the end to the middle part of its end onthe framework, and pivotally connectstroke, and to be carried from said fulcrum ed at the other end with the joint between the during the movement from the middle to the pitman b and links c, substantially as and for end of the stroke in both directions, substanthe purpose described. 15 5 tially as described. In testimony whereof I have signed my 3. The combination of the needlefbar lename to this specification in the presence of ver a, and its fulcrum a2; and links c pivottWo subscribing Witnesses.

ally connected to one end thereof; With the HERBERT H. BUFFUM. main shaft, and actuating-pitman b, connect- Witnesses: 1o ed by a pivotal joint with said links c; the H. J. LIVERMORE,

forked guide-link d pivotally supported at one JAS. J'. MALONEY. 

